MADISON—A Colorado woman was convicted Thursday of kidnapping her newborn nephew in Wisconsin and abandoning him in freezing temperatures outside an Iowa gas station as police closed in.

A federal jury deliberated for about three hours before finding Kristen Smith, 31, guilty of kidnapping, a charge that carries a sentence of 25 years to life in prison.

The Aurora, Colorado, woman took 4-day-old Kayden Powell from the Town of Beloit, Wisconsin, home where his parents were staying on Feb. 6. Smith testified that the parents were planning to move in with her in the next few days and the groggy father asked her to take the baby with her when she left at 2 a.m.

Prosecutors dismissed the explanation as ludicrous, saying no first-time parents would let someone take their newborn in the middle of the night without formula, diapers or clothes. They accused Smith of trying to steal a baby to pass off as her own.

Defense attorney Matthew Noel said the government misinterpreted her motives. He said she would have no reason to steal a child because she already had four children and a stepchild.

As Smith was driving back to Colorado that morning, the baby's mother called, frantic at her baby's disappearance. An officer who was at the house took the phone and asked Smith to pull over and wait for officers to question her.

Smith swaddled the baby, put him in a plastic tote, closed the lid and stashed the container at a gas station. Then she drove to another gas station about 500 yards away to meet an officer. She repeatedly denied knowing where the baby was.

She testified that she lied to officers out of panic, but prosecutors countered during closing arguments that if she truly had permission from the baby's father she had no reason to be afraid.

The baby, who was left in freezing temperatures for 29 hours, was found alive and safe by an Iowa police chief.